Keywords

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Scientific Name

Piper nigrum L.

Synonyms

Muldera wightiana Miq., Muldera multinervis Miq., Piper aromaticum Lam., Piper trioicum Roxb.

Family

Piperaceae

Common/English Names

Black Pepper, Green Pepper, Indian Pepper, Pepper, White Pepper.

Vernacular Names

  • Albanian: Piper;

  • Amharic: Kundo Berbere;

  • Arabic: Filfil, Fulful, Fulful Aswad;

  • Armenian: Bghbegh, Pghpegh;

  • Azeri: Bibər, İstiot, Qara Istiot;

  • Basque: Piper;

  • Belarusian: Čorny Perac, Perac;

  • Brazil: Pimenta-Da-Índia, Pimenta-Do-Reino;

  • Burmese: Nayukon, Nga Youk Kuan, Ngayok-kaung;

  • Bulgarian: Cheren Piper, Piper, Pipereni Zurna;

  • Catalan: Pebre, Pebre Negre;

  • Chinese: Bai Hu Jiao, Hak Wuh Jiu, Hei Hu Jiao, Hu Chiao, Hu Jiao, Woo Jiu;

  • Croatian: Biber, Crni Papar, Papar;

  • Czech: Černý Pepř, Pepř, Pepřovník Černý;

  • Danish: Peber, Sort Peber;

  • Dutch: Peper, Zwarte En Witte Peper, Zwarte Peper;

  • Eastonian: Must Pipar, Pipar;

  • Esperanto: Nigra Pipro, Pipro;

  • Finnish: Mustapippuri, Pippuri, Valkopippuri, Viherpippuri;

  • French: Poivre Blanc, Poivre Commun, Poivre Noir;

  • Frisian: Piper;

  • Gaelic: Piobar, Piobar Dubh;

  • Galician: Pementa;

  • Georgian: P’ilp’ili, Pilpili, P’eritsa, Pertisa, Shavi P’ilp’ili, Shavi P’eritsa;

  • German: Grüner Pfeffer, Pfeffer, Schwarzer Pfeffer; Weißer Pfeffer;

  • Greek: Peperi, Pipéri, Piperi Mauro;

  • Hebrew: Pilpel, Pilpel Shahor;

  • Hungarian: Bors, Borscserje, Fekete Bors, Fűszerbors;

  • Icelandic: Pipar, Svartur Pipar;

  • India: Jaluk, Gol Morich (Assamese), Golmarich, Gulmorich, Kaalaamorich, Kalomarich (Bengali), Aseymirus (Dhivehi), Kali Mirch (Dogri), Kaalaamirich, Kaalaamirii, Kalamiri, Klamirich, Kalomirich, Mari (Gujarati), Golmirch, Gulki, Kaalii Mirch, Malimirch (Hindu), Menasinaballii, Mensinballi, Menasina, Menasina-Kallu, Menasin Kallu, Menasu, Menusu. (Kannada), Kurumilagu, Kuru Mulagu, Kurumulaku, Nallamulaku, Yavanapriyam (Malayalam), Kaaliimirii, Mire (Marathi), Gola Maricha, Kala Marichamaricha (Oriya), Kali Marich, Kali Mirch (Punjabi), Maricha, Vella, Krishnan, Krishnadi (Sanskrit), Milagoo, Milaagu, Yavanappiriyam (Tamil), Miryaalatiga, Miryalatige, Miriyaalu, Miriyamu, Savyamu (Telugu), Kalimirch (Urdu)

  • Indonesia: Marica, Marica Hitam, Micha (Javanese), Lada Pedes (Sudanese), Lada, Lado Ketek, Lada Kobon (Sumatra);

  • Irish: Piobar;

  • Italian: Pepe, Pepe Nero;

  • Japanese: Burakku Peppaa, Koshou, Pepaa, Peppaa;

  • Kashmiri: Marts;

  • Kazakh: Burış;

  • Khmer: Môrech, Mrech;

  • Korean: Huchunamu, Pullaek Pepo, Pepeo-Bullaek;

  • Latvian: Melnie Pipari;

  • Lithuanian: Juodieji Pipirai;

  • Laotian: Mak Phik Noi, Phi Noi, Phik Noy, Phik Thai;

  • Macedonian: Crn Piper;

  • Malaysia: Lada, Lada Hitam, Lada Putih, Lada Sula;

  • Maltese: Bżar;

  • Nepali: Kalo Marichmarich;

  • Newari: Haku Male, Male;

  • Norwegian: Pepper, Svart Pepper;

  • Ossetian: Byrts, Tsyvzy;

  • Persian: Felfel Siah;

  • Philippines: Paminta (Tagalog);

  • Polish: Czarny Pieprz, Pieprz;

  • Portuguese: Pimenta, Pimenta Negra;

  • Provençal: Pebre, Peure;

  • Romanian: Piper, Piper Negru;

  • Russian: Perets Bélyi, Perets Chërnyi, Pjerets, Zelyony Pjerets;

  • Serbian: Papar, Biber;

  • Spanish: Pimentero Común, Pimienta, Pimienta Negra, Pimineta Nigra;

  • Sri Lanka: Gammiris, Miris (Sinhalese);

  • Slovašcina: Črni Poper, Poper;

  • Slovencina: Peprovnik;

  • Swahili: Pilipili;

  • Swedish: Peppar, Svart Peppar;

  • Tajik: Murch;

  • Thai: Phrik Thai;

  • Tibetan: Nalesham; Pho ba ril bu;

  • Turkish: Kara Biber, Siah Biber;

  • Turkmen: Burç;

  • Ukranian: Peets;

  • Vietnamese: Cây Tiêu, Hạt-Tiêu, Hồ Tiêu, Tiêu;

  • Yiddish: Fefer.

Origin/Distribution

The species is a native of the dense evergreen forests of the Western Ghats in South West India, now widely cultivated pantropically. The major producing countries are India, Indonesia, Sarawak, Malaysia and Brazil. It is also cultivated also in Sri Lanka, Myanmar, Thailand, Cambodia, Laos, Vietnam, New Guinea, on many Pacific islands, the Antilles, Madagascar, Zanzibar and in West Africa (Ghana to Angola).

Agroecology

Pepper thrives in warm areas with 1,750–2,500 mm annual rainfall and temperatures around 25–30°C and humidity above 85%. It grows in full sun or partial shade on well-composted, moist, well-drained, fertile soils rich in organic matter. It is drought and frost sensitive and abhors waterlogged soil. Black pepper is a tropical vine and needs artificial support (wooden, timber, cement) or trunk of live tree as support.

Edible Plant Parts and Uses

Pepper was the first spice to be traded globally and is the most important spice traded in terms of quantity and value.

Ripe and unripe berries and dried berries are used as spice in many food dishes. Dried fruits are called peppercorns. Dried ground pepper or whole peppercorn represent one of the most common spices in European and Asian cuisine. Depending on harvest time and processing, peppercorns can be black, white, green and red (actually, reddish brown) (Plates 3, 4, 5 and 6). The traditional types are black and white – the pepper of commerce and are used universally for flavouring food. Black and white pepper is used in various dishes for seasoning – white pepper in sauces or porridge, with mash potatoes and black pepper with steak or red meat. White pepper is popularly used in Western cooking, commonly recommended for white (cream-based) sauces and in conjunction with fish dishes such as gefilte stuffed fish. Dried green peppercorns are a more recent innovation, but are now rather common in Western countries. Red peppercorns, however, are still a very rare commodity. Red peppercorns are prepared from reddish brown ripe berries by drying or freeze drying of ripe berries. Black pepper is produced from the still-green mature but unripe berries. The berries are cooked briefly in hot water, both to clean them and to prepare them for drying. Drying is usually done in the sun for a few days or by a drying machine – oven or microwave. Once dried, black pepper or black peppercorn is produced. White pepper is processed from ripe berries by removal of the fruit pulp by soaking the berries in water for several days to a week and drying the seed. Green pepper, like black, is made from the unripe berries. Dried or dehydrated green peppercorns are treated in a manner that retains the green colour, such as treatment with sulphur dioxide or freeze drying. Fresh, unpreserved green pepper berries are also used in many Asian cuisine particularly Thai cuisines and are excellent in Thai stir-fries, Thai curries and Thai curry paste. Their flavour is described as piquant, fresh and with a bright aroma. Green pepper is also used in Western cooking, often incorporated into mustard or bottled condiments. Pickled peppercorns, also green, are unripe berries preserved in brine or vinegar and are often used as a spicy accompaniment to cold foods.

Other value added products of pepper include lemon pepper, garlic pepper, sauces and marinades that have pepper as the vital and main ingredient, pepper paste, pepper mayonnaise, pepper tofu, pepper cookies, pepper sweets, pepper toffees and pepper candies, pepper-flavoured crackers, pepper-flavoured fish and prawn crackers. Pepper is also used to flavour certain beverages and liquors such as pepper tea, pepper coffee, pepper flavoured milk, pepper flavoured puddings and pepper flavoured ice cream. Pepper oil and or piperine are added to certain liquors to impart a pungent and exotic taste and aroma. Double encapsulated pepper products are also available. The contained flavour or aroma is released only at high temperatures such as during steam cooking or baking. Pepper oil and or oleoresin are blended in vegetable oil or hydrogenated fat called fat-based pepper for use in products such as mayonnaise. Pepper oleoresin is also used in the meat processing industry.

Botany

Perennial woody climber up to 4 m high. The pepper plant is normally grown with support, either on a living tree or a post (which can be made of cement or wood) or trellis. Robust glabrous, woody stem with distinct enlarged nodes and rooting at the nodes. It has a shallow root system. Two types of branches are produced, vegetative (climbing) and reproductive (fruiting). Leaves alternate, simple, entire, ovate to ovate-oblong, 10–15  ×  5–9 cm, thick, more or less leathery, glabrous, base rounded, usually slightly oblique, apex acute; veins 5–7(–9), reticulate veins prominent (Plates 1 and 2). Petiole 1–2 cm Flowers polygamous, usually monoecious, small produce on pendulous Spikes which are leaf-opposed, peduncle bracts spatulate-oblong, 3–3.5  ×  ca. 0.8 mm, adaxially adnate to rachis, only margin and broad, rounded apex free, shallowly cupular. Stamens 2, 1 on each side of ovary; filaments thick, short; anthers reniform. Ovary globose; stigmas 3 or 4, rarely 5. Drupe green borne in cluster (spike) 20–30 cm long (Plates 1, 2 and 3), becoming red when ripe, drying black when unripe (Plate 6), globose, 3–4 mm in diam., sessile containing a single seed.

Plate 1
figure a

Pepper vine growing on a tree trunk with green pepper berries

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Plate 2
figure b

Pepper berries and leaves

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Plate 3
figure c

Green peppercorns (berries)

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Plate 4
figure d

White peppercorns

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Plate 5
figure e

Black peppercorns

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Plate 6
figure f

Close-up of white, red and black peppercorns

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Nutritive/Medicinal Properties

Analyses carried out in the United States (2011) reported black pepper (spice) to have the following proximate composition minus piperine (per 100 g value): water 12.46 g, energy 251 kcal (1,050 kJ); protein 10.39 g, total lipid 3.26 g, ash 4.49 g, carbohydrates 63.95 g, total dietary fibre 25.3 g, total sugars 0.64 g, sucrose 0.02 g, glucose 0.24 g, fructose 0.23 g, galactose 0.15 g, Ca 443 mg, Fe 9.17 mg, Mg 171 mg, P 158 mg, K 1,329 mg, Na 20 mg, Zn 1.19 mg, Cu 1.330 mg, Mn 12.753 mg, F 34.2 μg, Se 4.9 μg, vitamin C 0 mg, thiamine 0.108 mg, riboflavin 0.180 mg, niacin 1.143 mg, pantothenic acid 1.399 mg, vitamin B-6 0.291 mg, total folate 17 μg, choline 11.3 mg, betaine 8.9 mg, vitamin A 547 IU (27 μg RAE), α-carotene 12 μg, β-carotene 310 μg, β-cryptoxanthin 25 μg, lycopene 20 μg, lutein  +  zeaxanthin 454 μg, vitamin E (α-tocopherol) 1.04 mg, γ-tocopherol 6.56 mg, vitamin K (phylloquinone) 163.7 μg; total saturated fatty acids 1.392 g, 6:0 0.012 g, 8:0 0.102 g, 10:0 0.036 g, 12:0 0.093 g,14:0 0.030 g, 16:0 0.533 g, 18:0 0.327 g; total monounsaturated fatty acids 0.739 g, 14:1 0.016 g, 16:1 undifferentiated 0.077 g, 18:1 undifferentiated 0.647 g, 18:1 c 0.647 g; total polyunsaturated fatty acids 0.998 g, 18:2 undifferentiated 0.694 g, 18:3 undifferentiated 0.152 g, 18:3 n-3 c,c,c (ALA) 0.152 g, 20:3 undifferentiated 0.152 g; phytosterols 92 mg; tryptophan 0.058 g, threonine 0.244 g, isoleucine 0.366 g, leucine 1.014 g, lysine 0.244 g, methionine 0.096 g, cystine 0.138 g, phenylalanine 0.446 g, tyrosine 0.483 g, valine 0.547 g, arginine 0.308 g, histidine 0.159 g, alanine 0.616 g, aspartic acid 1.413 g, glutamic acid 1.413 g, glycine 0.441 g, proline 1.413 g, and serine 0.409 g.

Analyses carried out in the United States reported white pepper to have the following proximate composition minus piperine (per 100 g value): water 11.42 g, energy 296 kcal (1,238 kJ); protein 10.40 g, total lipid 2.12 g, ash 1.59 g, carbohydrates 68.61 g, total dietary fiber 26.2 g, Ca 265 mg, Fe 14.1, Mg 90 mg, P 176 mg, K 73 mg, Na 5 mg, Zn 1.13 mg, Cu 0.910 mg, Mn 4.3 mg, Se 3.1 μg, vitamin C 21 mg, thiamine 0.022 mg, riboflavin 0.126 mg, niacin 0.212 mg, vitamin B-6 0.1 mg, total folate 10 μg, total saturated fatty acids 0.626 g, total monounsaturated fatty acids 0.789 g, total polyunsaturated fatty acids 0.616 g, phytosterols 55 mg (USDA 2011).

There is a difference in the nutrient composition and levels between black and white pepper which reflect on the maturity and ripeness of the harvested berries and the way the pepper berries are processed to form black and white pepper. Black pepper is produced from the still-green unripe berries. The berries are cooked briefly in hot water, both to clean them and to prepare them for drying. Drying is usually done in the sun for a few days or by a drying machine – oven or microwave. Once dried, black pepper or black peppercorn is produced. White pepper is processed from ripe berries by removal of the fruit pulp by soaking the berries in water for several days to a week and drying the seed.

Black pepper contain higher levels of the minerals, vitamins than white pepper and also contain b-carotene, b-cryptoxanthin, lycopene, lutein and zeaxanthin.

Other Phytochemicals

Pepper Fruit

Some major sesquiterpene hydrocarbon constituents of black pepper were identified as δ-elemene, α-copaene, β-elemene, α-cis-bergamotene, α-santalene, α-trans-bergamotene, β-caryophyllene, α-humulene, β-selinene, α-selinene, β-bisabolene, δ-cadinene and calamine (Muller and Jennings 1967). Some minor volatile sesuqi­terpene hydrocarbons identified from black pepper were: α-cubebene, isocaryophyllene and γ-muurolene and a major constituent was identified as β-farnesene (Muller et al. 1968). The following optically active monoterpenes: (±)-linalool, (+)-α-phellandrene, (–)-limonene, myrcene, (–)-α-pinene, 3-methylbutanal and methylpropanal were identified as the most potent odorants of black pepper (Jagella and Grosch 1999a). Additionally, 2-isopropyl-3-methoxypyrazine and 2,3-diethyl-5-methylpyrazine were detected as important odorants of a black pepper sample with a mouldy, musty off-flavour. Nineteen odorants were quantified in white pepper (Jagella and Grosch 1999b). These included limonene, linalool, α-pinene, 1,8-cineole, piperonal, butyric acid, 3-methylbutyric acid, methylpropanal, and 2- and 3-methylbutanal as key odorants of white pepper. The faecal off-flavour was caused by skatole and was enhanced by the presence of p-cresol. Oxygenated compounds isolated from black pepper included: linalool, 1-terpinen-4-ol, α-terpineol, cryptone, carvone, ρ-cymene-8-ol, trans-carveol, cis-carveol, safrole, ar-curcumene, methyl eugenol, nerolidol and myristicin (Russell and Jennings 1969). Piperine, a pungent component of black pepper oleoresin was isolated and its structure elucidated as trans-5-(3,4-methylenedioxyphenyl)-2-pentenoic acid piperidide (Traxler 1971).

Piper nigrum fruit had been reported to contain alkamides: N-trans-feruloyltyramine, coumaperine (Nakatani et al. 1980), guineensine (Nakatani and Inatani 1981), N-isobutyl amide of octadeca-trans-2-cis-4-dienoic acid (Siddiqui et al. 1997), dipiperamides A, B, C, D, E, retrofractamide A, brachyamide A, neopellitorine B, richolein, ilepcimide (Tsukamoto et al. 2002a, b), a pyrrolidine, isopiperolein B (Srinivas and Rao 1999), piperamide, guineensine (Singh et al. 2004), 2E, 4E, 8Z-N-isobutyleicosatrienamide, pellitorine, trachyone, pergumidiene, isopiperoleine B (Reddy et al. 2004), pipsaeedine, pipbinine, piptaline (Siddiqui et al. 2004b), kalecide, sarmentine, chingchengenamide, pipnoohine, pipyahyine (Siddiqui et al. 2004c), piperine, piperoleines A, B, piperyline, piperanine, pipercide, feruperine, pipernonaline, dehydropipernonaline, nigramide R pipercyclobutanamide A, (Subehan et al. 2006), retrofractamide A, pipercide, piperchabamide D, pellitorin, dehydroretrofractamide C and dehydropipernonaline (Rho et al. 2007), guineensine, retrofracamide C, (2E,4Z,8E)-N-[9-(3,4-methy­lenedioxyphenyl)-2,4,8-nonatrienoyl]piperidine, pipernonaline, piperrolein B, piperchabamide D, pellitorin and dehydropipernonaline (Lee et al. 2008); flavonoids: glycosides of kaempferol, rhamnetin and quercetin in considerable concentration, and a lesser amount of isorhamnetin (Voesgen and Herrmann 1980); alkaloids: pipercyclobutanamides A and B (Fujiwara et al. 2001); and lignans: hinokinin (Tsukamoto et al. 2002a, b).

The following major aroma compounds were found in black pepper: germacrene D (11.01%), limonene (10.26%), β-pinene (10.02%), α-phellandrene (8.56%), β-caryophyllene (7.29%), α-pinene (6.40%) and cis-β-ocimene (3.19%) (Jirovetz et al. 2002). The main compounds such as β-caryophyllene, germacrene D, limonene, β-pinene, α-phellandrene and α-humulene, as well as minor constituents such as δ-carene, β-phellandrene, isoborneol, α-guaiene, sarisan, elemicin, calamenene, caryophyllene alcohol, isoelemicin, T-muurolol, cubenol and bulnesol, were of greatest importance for the characteristic pepper odor notes. Further aroma impressions were attributed to mono- and sesquiterpenes, hexane, octane and nonane derivatives. Musenga et al. (2007) extracted 11 aromatic and terpenic compounds namely terpinen-4-ol, caryophyllene oxide, limonene, α-pinene, 3-carene, β-pinene, αa-humulene, β-caryophyllene, α-phellandrene, eugenol and piperine from pepper extracts using capillary electrochromatography.

Black pepper was found to contain about 5–9% of the alkaloids piperine and piperettine and about 1–2.5% of volatile oil, the major constituents of which are α and β-pinene, limonene, and phellandrene (Tewtrakul et al. 2000). The main pungent principle in the green berries of pepper was piperine. Generally the piperine content of black or white peppercorns varied within the range of 3–8 g/100 g, whereas the content of the minor alkaloids piperyline and piperettine was estimated as 0.2–0.3 and 0.2–1.6 g/100 g, respectively (Tainter and Grenis 1993). Other alkaloids present included chavicine, isopiperine and isochavicine and minor alkaloids piperalin A, pieralein B, piperanine (Wood et al. 1988). The acetone extract of pepper showed the presence of 18 components accounting for 75.59% of the total amount; piperine (33.53%), piperolein B (13.73%), piperamide (3.43%) and guineensine (3.23%) were the major components (Singh et al. 2004). Piperine is known to be the pungent principle in black and white ground pepper and green whole pepper berries (Schulz et al. 2005). It was found that piperine occurs more or less in the whole perisperm of the green fruit. Recovery of piperine from dried fruit powder was in the high range of 98.57–97.25% from P. nigrum and 96.50–97.50% from P. longum (Hamrapurkar et al. 2011).

Piptigrine was isolated from the dried ground seeds of Piper nigrum along with the known amides piperine and wisanine (Siddiqui et al. 2004a). The petroleum ether and ethyl acetate fractions of dried ground seeds of Piper nigrum afforded 16 compounds (1–16) including one new insecticidal amide, pipwaqarine (1) and six constituents (3,4,6,7,11,15) previously unreported from this plant. (Siddiqui et al. 2005). Studies on the petroleum ether soluble and insoluble fraction of ethanol extract of dried ground seeds of Piper nigrum resulted in the isolation and structure elucidation of one new and 11 known compounds which included three hitherto unreported constituents, namely, cinnamylideneacetone, 3,4-methy­lenedioxyphenylpropiophenone and 2-hydroxy-4,5-methylenedioxypropiophenone (Siddiqui et al. 2008).

Using vibrational microscopy Schulz et al. (2005) found the following contents (in mg/100 g) for piperine 2.75–5.07, essential oil 0.80–3.60 and terpenoids in black and white peppers: α-pinene nd (not determined) -0.18, β-pinene 0.003–0.29, sabinene nd-0.75, myrcene nd-0.08, α-phellandrene nd-0.16, δ-3-carene 0.005–0.80, limonene 0.01–0.52, β-caryophyllene 0.26–1.22, caryophyllene oxide 0.005–0.14. The following terpenoids were detected in hydrodistilled pepper oils: α-pinene 0.26–5.39, β-pinene 0.69–11.96, sabinene nd-20.9, myrcene 0.21–3.26, α-phellandrene nd-6.61, δ-3-carene 0.72–32.65, limonene 1.64–22.48, β-caryophyllene 12.84–65.68, caryophyllene oxide 0.22–8.35.

Pepper Essential Oil

Pepper oil contains a complex mixture of monoterpenes (70–80%), sesquiterpenes (20–30%), and small amounts of oxygenated compounds, with no pungent principles present. Concentration and composition vary, depending on sources, cultivars and methods of extraction.

Some physical and chemical properties of black pepper berries were reported as follows: oleoresin 10.6 wt%, piperine 5.8 wt%, essential oil 1.7(v/w)%, water content 11 wt%, real density 1,545 kg/m3, bulk density 793 kg/m3 and bed porosity 0.49 (Kumoro et al. 2010). Pepper essential oil was found to be a mixture consisting of 90% hydrocarbons and 10% oxygenated terpenes and aromatic compounds (Ferreira et al. 1999). The hydrocarbon fraction was composed of monoterpenes (70–80%) and sesquiterpenes (20–30%), which appeared to possess the desirable attributes of pepper flavor. Though oxygenated terpenes were relatively minor constituents, they contributed to the characteristic odor of pepper oil (Pino et al. 1990). They detected 46 components including (E)-β-ocimene, δ-guaiene, (Z) (E)-farnesol, δ-cadinol and guaiol, which were reported for the first time. Constituents of black pepper essential oil (% area) detected by hydrodistillation and supercritical fluid extraction using carbon dioxide (values in brackets) (Kumoro et al. 2010) included: monterpenes:- α-tujene 0.45 (0.43), α-pinene 2.15 (1.80), sabinene 4.80 (5.50), β-pinene 4.20 (3.50), δ-carene 4.30 (5.00), limonene 6.30 (6.80); oxygenated monoterpenes:- linalool 0.59 (1.30), myrtenol 0.27 – (nd), caryone 0.29 – (nd); sesqueterpenes:- δ-elemene 0.30 (0.23), α-cubebene 0.38 (0.52), α-copaene 5.40 (6.85), calarene 2.20 (2.70), δ-gurjunene 0.30 (2.65), β-caryophyllene 2.36 (12.40), α-humulene 0.48 (3.30), α-selinene 2.65 (3.70), δ-cadinene 2.15 (3.75); oxygenated sesqueterpenes:- elemol 7.96 (6.40), caryophyllene oxide 12.50 (7.94) and β-eudesmol 3.90 (1.80).

Wrolstad and Jennings (1965) identified the following monoterpenes in the volatiles of black pepper oil: α-pinene, β-pinene, sabinene, β-carene, limonene, ρ-cymene, α-thujene, α-phellandrene, myrcene, β-phellandrene, γ-terpinene, and terpinolene. Schulz et al. (2005) reported the volatile fraction of pepper oil to be dominated by monoterpene hydrocarbons (30–70%) such as α- and β-pinene, limonene, sabinene, myrcene, α-phellandrene, and δ-3-carene. Sesquiterpenes such as α- and β-caryophyllene and β-farnesene made up 25–45% of the total essential oil content, whereas oxygen-containing sesquiterpenes such as caryophyllene oxide occurred in amounts of 4–14%. The pinenes possessed a turpentine eucalyptus- like smell, whereas the odour of the other monoterpenes was described as fresh and pine-needle-like. Generally the so-called “top-peppery note” was assigned to the monoterpene group; the “pepper odor” to the sesquiterpenes, and the oxygen-containing sesquiterpenes were responsible for the “body” of the pepper aroma. Kapoor et al. (2009) found 54 volatile components that amounted to 96.6% of the total weight of pepper essential oil. β-caryophyllene (29.9%) was found as the major component along with limonene (13.2%), β-pinene (7.9%), sabinene (5.9%), and several other minor components. The major component of both ethanol and ethyl acetate oleoresins was found to contain piperine (63.9% and 39.0%), with many other components in lesser amounts.

Monoterpene hydrocarbons of black pepper oil were isolated and identified as α-pinene, β-pinene, sabinene, β-carene, limonene, and p-cymene. α-thujene, α-phellandrene, myrcene, β-phellandrene, γ-terpinene, and terpinolene were also found (Wrolstad and Jennings 1965). The monoterpenes isolated also contained small quantities of α-terpinene and greater quantities of γ-terpinene, p-cymene, and terpinolene. Cis-p-2-methen-1-ol, cis-p-2,8-menthadien-1-ol and transpinocarveol was detected in black pepper oil (Richard and Jennings 1971). m-mentha-3(8),6-diene (isosylveterpinolene) was found to the extent of 0.12–0.17% in black and green pepper oil (Nussbaumer et al. 1999).

Ninety four percent of the compounds were identified in fresh pepper berry oil (Sasidharan and Menon 2010). Limonene was the predominant compound (18%), followed by β-pinene (14.2%), and β-caryophyllene (13.2%). Monoter­pene hydrocarbons accounted for 54.4% and some of the major monoterpene hydrocarbons were α-pinene (12.1%), α-thujene (1.5%), δ-3-carene(3.2%), and sabinene (3.3%). monoterpene oxygenated compounds amounted to 5.1%, and some of the compounds identified were linalool, terpinen-4-ol, and α-terpineol. The total sesquiterpene hydrocarbon content was 20.3% of which the main compound was β-caryophyllene (13.2%), followed by α-humulene (1.6%), cuparene (2.7%), δ-cadinene (0.7%). The total sesquiterpene oxygenated compounds content was 14.8% of which the main (E)-nerolidol (4.1%) was the main compound followed by Farnesol (Z,E) (2.1%).

Ninety six percent of the compounds were found in dry pepper berry oil (Sasidharan and Menon 2010). The main compound was β-caryophyllene (20.4%), followed by limonene (16%). The monoterpene hydrocarbon content came down to 46.7%. α- and β- pinenes, δ-3-carene, p-cymene, camphene were some of the monoterpene hydrocarbons. Monoterpene oxygenated compounds amounted to 2.4%. The sesquiterpene hydrocarbon compounds content constituted 45.4% of which β-caryophyllene was the main compound, and followed by α-humulene (2.8%), α-copaene (1.9%), α-guaine (2%), δ-guaine (1.6%), β-bisabolene (2.1%), cuparene (3.5%). The sesquiterpene oxygenated compounds amounted to 1.9%. Liu et al. (2007) separated and identified 30 compounds from the essential oil of P. nigrum. The main components were β-caryophyllene (23.49%), δ-3-carene (22.20%), D-limonene (18.68%), β-pinene (8.92%) and α-pinene (4.03%).

Fifty-five compounds were identified in the oils of four major cultivars of black pepper from Kerala viz. Thevanmundi, Poonjaranmunda, Valiakaniakadan, and Subhakara (Jayalekshmy et al. 2003). The main components of Thevanmundi oil were sabinene (4.5–16.2%), β-pinene (3.7–8.7%), limonene (8.3–18.0%) and β-caryophyllene (20.3–34.7%). Poonjaranmunda oil contained as major compounds β-pinene (6.0–11.7%) limonene (14.9–15.8%), β-ocimene. Forty-nine components accounting for 99.39% of the total amount was identified in pepper oil, and the major components were β-caryophyllene (24.24%), limonene (16.88%), sabinene (13.01%), β-bisabolene (7.69%) and α-copaene (6.3%) (Singh et al. 2004). Fifty-five compounds were identified in the oils of two major cultivars of black pepper from Kerala viz. Vellanamban and Sreekara and one Indonesian cultivar grown in Kutching in Kerala (Menon and Padmakumari 2005). The main components of vellanamban oil were sabinene (3.9–18.8%), β-pinene (3.9–10.9%), limonene (8.3–19.8%) and β-caryophyllene (28.4–32.9%). Sreekara oil contained as major compounds β-pinene (0–11.2%), limonene (20.1–22.1%) and β-caryophyllene (16.8–23.1%). Kutching oil contained α-pinene (2.3–5.4%), sabinene (6.7–13.3%), limonene (14.5–17.5%) and β-caryophyllene (20.8–39.1%). Clery et al. (2006) analysed the N-containing compounds in black pepper oil by capillary GC, GC/MS and HPLC techniques. The most abundant nitrogenous compounds were 1-formylpiperidine (28 ppm), 1-acetylpiperidine (22 ppm) and 2,3,5,6-tetramethylpyrazine (7 ppm). In addition to previously reported compounds, 20 previously unreported pyrazines, pyridines and piperidines were identified. Aroma assessment revealed that 2-ethyl-3,5-dimethylpyrazine (1.5 ppm; roasted green vegetable, coffee and cocoa notes) and 3-ethyl-2,5-dimethylpyrazine (490 ppb; earthy and roasty notes) contributed most significantly to the overall aroma.

Orav et al. (2004) found that the most abundant compounds in pepper oils were (E)-β-caryophyllene (1.4–70.4%), limonene (2.9–38.4%), β-pinene (0.7–25.6%), δ-3-carene (1.7–19.0%), sabinene (0–12.2%), α-pinene (0.3–10.4%), eugenol (0.1–41.0%), terpinen-4-ol (0–13.2%), hedycaryol (0–9.1%), β-eudesmol (0–9.7%), and caryophyllene oxide (0.1–7.2%). Green pepper corn obtained by a sublimation drying method gave more oil (12.1 mg/g) and a much higher content of monoterpenes (84.2%) in the oil than air-dried green pepper corn (0.8 mg/g and 26.8%, respectively). The oil from ground black pepper contained more monoterpenes and less sesquiterpenes and oxygenated terpenoids as compared to green and white pepper oils. After 1 year of storage of pepper samples in a glass vessel at room temperature, the amount of the oils isolated and the content of terpenes decreased, and the amount of oxygenated terpenoids increased. Different from other pepper samples, 1 year storage of green peppercorn raised the oil content more than twice of both drying methods. Fifty-four components representing about 96.6% of the total weight were found in black pepper essential oil (Kapoor et al. 2009). β-caryophylline (29.9%) was found as the major component along with limonene (13.2%), β-pinene (7.9%), sabinene (5.9%), and several other minor components. The major component of both ethanol and ethyl acetate oleoresins was found to contain piperine (63.9% and 39.0%), with many other components in lesser amounts. The antioxidant activities of essential oil and oleoresins of black pepper were evaluated against mustard oil by peroxide, p-anisidine, and thiobarbituric acid (Kapoor et al. 2009).

Fifty-five compounds were identified in the essential oil samples of four major black pepper cultivars the chemical composition of which varied widely due to variations in agroclimatic conditions and growing seasons (Menon et al. 2000). For example sabinene varied from 0.2% in cv. Subhakara to 17.1% in cv. Valiakaniakadan. Delta-3-carene varied from 0% in cv. Valiakaniakadan in 1990 to 23.4% in cv. Subhakara in 1991. Limonene varied from 8.3% in cv. Thevanmundi oil to 22.7% in cv Subhakra oil. Alpha-cubebene varied from 0.1% in cv. Poonjaranmunda oil (in the season 1990) and in cv. Subhakara oil (in the seasons 1990 and 1992) to 6.8% in cv. Thevanmundi oil (in the season 1992). Beta-caryophyllene, the main sesquiterpene hydrocarbon of the pepper oil, varied from 7.6% in cv. Subhakara (season 1990) sample to 38.4% in cv. Valiakaniakadan oil (season 1992). Elemol content varied from 0.7% in cv. Subhakara oil (season 1990) to 9.6% in cv. Thevanmundi oil (season 1992). Another oxygenated compound, caryophyllene oxide varied from 0.4% in cv. Subhakara oil (season 1991) and in cv. Poonjaranmunda oil (season 1991) to 6% in cv. Subhakara oil (season 1990). Studies by Liang et al. (2010) indicated that the chemical compositions of pepper essential oils were greatly influenced by different production areas. The main constituents in three kinds of pepper essential oils from different regions were: α-pinene; cyclohexene, 1-methyl-4-(1-methylethylidene)-; 3-cyclohexen-1-ol, 4-methyl-1-(1-methylethyl)-; β-pinene; limonen-6-ol, pivalate; (E)-3(10)-caren-4-ol; and trans-caryophyllene. Bicyclo[3.1.0]hexane, 4-methylene-1-(1-methyl­ethyl)-; isocaryophillene; and bufa-20,22-dienolide, 14-hydroxy-3-oxo-, (5á)- were detected only in essential oil of black pepper from Guang Dong province. 2-cyclohexen-1-ol, 1-methyl-4-(1-methylethyl)-, trans-caryophyllene; copaene; eudesma-4(14),11-diene; and trans-9-octadecenoic acid, trimethylsilyl ester were detected only in essential oil of black pepper from YunNan province. 1,2-dihydropyridine, 1-(1-oxobutyl)-; and 1-chloroeicosane were detected only in essential oil of black pepper from FuJian province.

Pepper Leaves

The pepper leaf oil was found to contain 63.3% sesquiterpene hydrocarbons and 32.4% sesquiterpene oxygenated compounds oil (Sasidharan and Menon 2010). The main compound of the oil was α-bisabolol (25.3%), followed by α-cubebene (20.2%). Some of the other compounds were β-bisabolene (15%), β-elemene (5.4%) and β-caryophyllene (4%). Sesquiterpene alcohols like elemol and nerolidols were also present in the oil. Pepper leaf was found to contain lignans: (-)-cubebin, (-)-3,4-dimethoxy-3,4-desmethylenedioxycubebin, (-)-3-desmethoxycubebinin (Matsuda et al. 2004).

About 50 compounds were identified in the stem and leaf oils of Piper nigrum (Pino et al. 2003), accounting for more than 99.8% and 99.5% of the oils, respectively. The leaf oil was dominated by globulol (49.7%) and α-pinene (21.7%), while the major components of the stern oil were β-caryophyllene (19.5%), α-pinene (19.3%), α-terpinene (12.71%) and globulol (12.6%). Young shoots and leaves contained only traces of piperine but consi­derable amounts of piperine (ca 0.2%) were found, however, in mature, fully differentiated shoots, reaching the contents of commercially available white or black pepper of lower quality (Semler and Gross 1988). Roots had about 0.03% piperine.

Pepper Roots

Seven new amide alkaloids, named N-isobutyl-4-hexanoyl-4-hydroxypyrrolidin-1-one (1), (±)-erythro-1-(1-oxo-4,5-dihydroxy-2E-decaenyl)piperidine (2), (±)-threo-1-(1-oxo-4,5-dihydroxy-2E-decaenyl)piperidine (3), (±)-threo-N-isobutyl-4,5-dihydroxy-2E-octaenamide (4), 1-(1,6-dioxo-2E,4E-decadienyl)piperidine (5), 1-[1-oxo-3(3,4-methylenedioxy-5-methoxyphenyl)-2Z-propenyl]piperidine (6), and 1-[1-oxo-5(3,4-methylenedioxyphenyl)-2Z,4E-pentadienyl]pyrrolidine (7), were isolated from the roots of Piper nigrum, together with 32 known amides that included piperine, isopiperine, fagaramide, piperettine, pellitorin, piperanine, kalecide, piperyline, piperoleine B, isochavicine, neopellitorine B, cinnamonpyrrolidide, piperettyline, tricholein, sarmentineilepcimide, pipernonaline, sarmentosine, brachyamide B, pipercycliamide (Wei et al. 2004b). Two phytosterols elucidated as stigmastane-3,6-dione and stigmast-4-ene-3,6-dione, were isolated from the roots of Piper nigrum (Wei et al. 2004a). Fifteen novel dimeric amide alkaloids possessing a cyclohexene ring, nigramides A-O (1–15), as well as four novel dimeric amide alkaloids possessing a cyclobutane ring, nigramides P-S (17–20), were isolated from the roots of Piper nigrum (Wei et al. 2005).

Black pepper (Piper nigrum) is used not only in human dietaries but also for a variety of other purposes such as medicinal, as a preservative, and in perfumery (Srinivasan 2007). All these uses can be attributed to its important major bioactive alkaloid, piperine. Dietary piperine, by favorably stimulating the digestive enzymes of pancreas, enhances the digestive capacity and significantly reduces the gastrointestinal food transit time. Pepper and piperine have also a diverse array of pharmacological properties such as antioxidant, anticancer, hepatoprotective, antiinflammatory, antidepressant, antiatherogenic, antihypertensive, drug potentiating and other activities elaborated below.

Antioxidant Activity

Volatile pepper oil and acetone pepper extract were identified as a better antioxidant for linseed oil, in comparison with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) (Singh et al. 2004). The hydrolyzed and nonhydrolyzed extracts of black pepper contained sig­nificantly more polyphenols compared with those of white pepper (Agbor et al. 2006). For either of these peppercorns, the hydrolyzed extract contained significantly more polyphenols compared with the nonhydrolyzed extract. A dose-dependent effect was observed in the free radical and reactive oxygen species scavenging activities of all the extracts, with the black pepper extracts being the most effective. Phenolic compounds from green pepper were found to have high antioxidant potential (Chatterjee et al. 2007). EC50 values of the major phenolic compounds of green pepper namely, 3,4-dihydroxyphenyl ethanol glucoside, 3,4-dihydroxy-6-(N-ethylamino) benzamide and phenolic acid glycosides were found to be 0.076, 0.27 and 0.12 mg/ml, respectively, suggesting a high radical scavenging (DPPH) activity of these phenolics. These phenolics also protected plasmid DNA damage upon exposure to gamma radiation as high as 5 kGy and inhibited lipid oxidation as revealed by β-carotene–linoleic acid assay. P. nigrum could be considered as a potential source of natural antioxidant (Singh et al. 2008). The free radical scavenging activity of the different fractions of petroleum ether extract of P. nigrum (PEPN) increased in a concentration dependent manner. In DPPH free radical scavenging assay, the activity of fraction R3 and R2 were found to be almost similar. The R3 (100 μg/ml) fraction 55.68% nitric oxide radicals generated from sodium nitroprusside. PEPN scavenged the superoxide radical generated by the xanthine/xanthine oxidase system. The fraction R2 and R3 in the doses of 1,000 μg/ml inhibited 61.04% and 63.56%, respectively. The amounts of total phenolic compounds were determined and 56.98 μg pyrocatechol phenol equivalents were detected in 1 mg of R3. P. nigrum was richest in glutathione peroxidase and glucose-6-phosphate dehydrogenase, green pepper was richest in peroxidase and vitamin C while vitamin E was more in P. longum and P. nigrum. Catalase activity was high in Piper longum, followed by Piper cubeba, green pepper, Piper brachystachyum and Piper nigrum. All the Piper species had GSH content of around 1–2 nM/g tissue. The antioxidant components of Piper species constitute a very efficient system in scavenging a wide variety of reactive oxygen species. Antioxidant potential of Piper species was further confirmed by their ability to suppress in-vitro lipid peroxidation by around 30–50% with concomitant increase in GSH content.

Studies indicated that carcinogens (7,12,dimethyl benzanthracene, dimethyl amino-methyl azobenzene and 3-methyl cholenthrene) treatment induced glutathione (GSH) depletion with substantial increase in thiobarbituric reactive substances and enzyme activities in male rats but piperine treatment with carcinogens resulted in inhibition of thiobarbituric reactive substances (Khajuria et al. 1998). Piperine mediated a significant increase in the GSH levels and restoration in gamma-GT and Na+-K+-ATPase activity. The data indicated a protective role of piperine against the oxidative alterations by carcinogens. The data suggested that piperine modulated the oxidative changes by inhibiting lipid peroxidation and mediating enhanced synthesis or transport of GSH thereby replenishing thiol redox. They further showed that Lipid peroxidation content, measured as thiobarbituric reactive substances (TBARS), was increased with piperine treatment although conjugate diene levels were not altered in the rat intestinal mucosa and epithelial cells (Khajuria et al. 1999). A significant increase in glutathione levels was observed, whereas protein thiols and glutathione reductase activity were not altered. The study suggested that increased TBARS levels may not be a relevant index of cytotoxicity, since thiol redox was not altered, but increased synthesis transport of intracellular GSH pool may play an important role in cell hemostasis.

The following phenolic amides: piperine (1), N-trans-feryloyl tyramine (2a) and its acetyl and methyl derivatives, diacetyl N-trans-feryloyl tyramine (2b), trimethyl N-trans-feryloyl tyramine (2c), coumaperine [N-5-(4-hydroxyphenyl)-2E,4E-pentadienoyl piperidine] (3a) and its derivative, acetyl coumaperine (3b), N-trans-feruloyl piperidine (4), N-5-(4-hydroxy-3-methoxyphenyl)-2E,4E-pentadienoyl piperidine (5), and N-5-(4-hydroxy-3-methoxyphenyl)-2E-pentenoyl piperidine (6) were identified from P. nigrum (Nakatani et al. 1986). All the phenolic amides possessed significant antioxidant activities that were more effective than the naturally occurring antioxidant, alpha-tocopherol at the same concentration (0.01%). One amide, feruperine, had antioxidant activity as high as the synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Naturally occurring antioxidants, therefore, may surpass BHA and BHT in their ability to inactivate mutagens in food.

Studies by Vijayakumar et al. (2004) indicated supplementation with black pepper or the active principle of black pepper, piperine, could reduce high-fat diet induced oxidative stress to the cells. Significantly elevated levels of thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and significantly lowered activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and reduced glutathione (GSH) in the liver, heart, kidney, intestine and aorta were observed in rats fed the high fat diet as compared to the control rats. Simultaneous supplementation with black pepper or piperine lowered TBARS and CD levels and maintained SOD, CAT, GPx, GST, and GSH levels to near those of control rats.

Both water extract (WEBP) and ethanol extract (EEBP) of black pepper exhibited strong total antioxidant activity in six different assay, namely, total antioxidant activity, reducing power, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radi­cal scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities (Gülçin 2005). The 75 μg/ml concentration of WEBP and EEBP showed 95.5% and 93.3% inhibition on peroxidation of linoleic acid emulsion, respectively. On the other hand, at the same concentration, standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and alpha-tocopherol exhibited 92.1%, 95.0%, and 70.4% inhibition on peroxidation of linoleic acid emulsion, respectively. The total phenolics content of water and ethanol extracts were determined by the Folin-Ciocalteu procedure and 54.3 and 42.8 μg gallic acid equivalent of phenols was detected in 1 mg WEBP and EEBP.

Both the black pepper oil and oleoresins showed strong antioxidant activity in comparison with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) but lower than that of propyl gallate (PG) (Kapoor et al. 2009). In addition, their inhibitory action by FTC method, scavenging capacity by DPPH (2,2′-diphenyl-1-picrylhydrazyl radical), and reducing power were also confirmed, proving the strong antioxidant capacity of both the essential oil and oleoresins of pepper.

The methanolic extracts of the leaves of three pepper spices (Piper guineense, Piper nigrum and Piper umbellatum) exhibited a marked polyphenolic concentration and dose dependent free radical scavenging activity (Agbor et al. 2007). The free polyphenolic concentration of the three spices was in the order P. umbellatum (15.9 mg/g)  >  P. guineense (12.6 mg/g)  >  P. nigrum (9.8 mg/g). The three Piper extracts exhibited a 79.8–89.9% scavenging effect on DPPH, an 85.1–97.9% scavenging effect on nitric oxide at a dose level of 10 mg/ml and a 47.1–51.6% scavenging effect on superoxide radical at a dose level of 8 mg/ml extraction. The Piper extracts also exhibited a 57–76.1% scavenging effect on hydroxyl radical at 5 mg/ml, a 0.4–0.6 reducing power and an 88.3–93.9% metal chelating activity at a dose level of 8 mg/ml of extract. Thus, these Piper species could play a role in the modulation of free radical induced disorders. High antioxidant (DPPH scavenging) activity was found in Piper cubeba ethanol extract 77.61% with IC50 value of 10.54 μg/ml compared to Piper nigrum 74.61% and IC50 value of 14.5 μg.ml (Nahak and Sahu 2011). P. cubeba had the highest total phenolic content of 123.1 μg/g compared to P. nigrum with 62.3 μg/g. P. cubeba was found to contain alkaloid, glycosides, steroid, flavonoid, tannins and antraquinones while P. nigrum contained the same plus terpenoid and reducing sugars.

Anticancer Activity

Administration of coumaperine from white pepper, to male F344 rats provided protection against the initiation stage of rat hepatocarcinogenesis induced by diethylnitrosamine (Kitano et al. 2000). This was attributed to inhibition of proliferation of proliferating cell nuclear antigen (PCNA)-positive cells. Studies demonstrated the antimetastatic activity of piperine, an alkaloid of Piper nigrum and Piper longum. Simultaneous administration of piperine with tumour induction by B16F-10 melanoma cells produced a significant reduction (95.2%) in tumour nodule formation in C57BL/6 mice (Pradeep and Kuttan 2002). Increased lung collagen hydroxyproline (22.37 μg/mg protein) in the metastasized lungs of the control animals compared to normal animals (0.95 μg/mg protein) was significantly reduced (2.59 μg/mg protein) in the piperine-treated animals. The high amount of uronic acid (355.83 μg/100 mg tissue) in the metastasized control animals was significantly reduced (65 μg/100 mg tissue) in the animals treated with piperine. Lung hexosamine content was also significantly reduced in the piperine-treated animals (0.98 mg/100 mg lyophilized tissue) compared to the untreated tumour-bearing animals (4.2 mg/100 mg lyophilized tissue). The elevated levels of serum sialic acid and serum gamma glutamyl transpeptidase activity in the untreated control animals was significantly reduced in the animals treated with piperine. The piperine-treated animals even survived the expe­riment (90 days). Histopathology of the lung tissue also correlated with the lifespan of the drug-treated animals. In another study, piperine was found to inhibit production of nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha) level using in-vitro as well as in-vivo systems (Pradeep and Kuttan 2003). The level of nitrite in the LPS stimulated Balb/C mice (95.3 μM) was reduced in the piperine treated animals (25 μM) significantly. Nitrite level in the Concanavalin-A (Con-A) treated control animals (83.1 μM) was also significantly reduced to 18 μM in the piperine treated mice. The drastically elevated levels of TNF-alpha in the lipopolysaccharide (LPS) stimulated animals (625.8 μg/ml) was lowered in the piperine treated animals (105.8 μg/mL). Piperine also inhibited the Con-A induced TNF-alpha production. Piperine could inhibit the nitrite production by in-vitro activated macrophages (116.25 μM) to the normal level (15.67 μM) at concentration of 5 μg/ml. In-vitro L929 bioassay also revealed the inhi­bition of TNF-alpha production by the piperine treatment.

Piplartine {5,6-dihydro-1-[1-oxo-3-(3,4,5-trimethoxyphenyl)-trans-2-propenyl]-2(1 H)pyridinone} and piperine {1-[5-(1,3-­benzodioxol-5-yl)-1-oxo-2,4-pentadienyl]piperidine} were found to display cytotoxicity in the brine shrimp lethality assay, sea urchin eggs development, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2 H-tetrazolium bromide (MTT) assay using tumour cell lines and lytic activity on mouse erythrocytes (Bezerra et al. 2005). Piperine showed higher toxicity in brine shrimp (DL50  =  2.8 μg/ml) than piplartine (DL50  =  32.3 μg/ml). Both piplartine and piperine inhibited the sea urchin eggs development during all phases examined, first and third cleavage and blastulae, but in this assay piplartine was more potent than piperine. In the MTT assay, piplartine was the most active with IC50 values in the range of 0.7–1.7 μg/ml. In subsequent study, Bezerra et al. (2006) found that piperine and piplartine inhibited solid tumour development in mice transplanted with Sarcoma 180 cells. The inhibition rates were 28.7% and 52.3% for piplartine and 55.1% and 56.8% for piperine, after 7 days of treatment, at the lower and higher doses, respectively. The antitumour activity of piplartine was related to inhibition of the tumour proliferation rate but piperine did not inhibit cell proliferation as observed in Ki67 immunohistochemical analysis. Histopathological analysis of liver and kidney showed that both organs were reversibly affected by piplartine and piperine treatment, but in a different way. Piperine was more toxic to the liver, leading to ballooning degeneration of hepatocytes, accompanied by microvesicular steatosis in some areas, than piplartine which, in turn, was more toxic to the kidney, leading to discrete hydropic changes of the proximal tubular and glomerular epithelium and tubular hemorrhage in treated animals. In further study, piplartine was found to enhance the therapeutic effectiveness of chemotherapeutic drugs and that the combination of 5-fluorouracil (5-FU) with piplartine or piperine could improve immunocompetence hampered by 5-FU (Bezerra et al. 2008). The results indicated that either piplartine- or 5-FU-treated animals showed a low inhibition rate when they were used individually at low doses of 28.67% and 47.71%, respectively, but when they were combined at the same dose, the inhibition rate increased significantly to 68.04%. Piplartine was also found to suppress leukemia growth and reduce cell survival, triggering both apoptosis and/or necrosis, depending on the concentration used (Bezerra et al. 2007). The antiproliferative activity of piplartine appeared to be related to the inhibition of DNA synthesis. Piplartine-mediated reduction in cell number was associated with an increasing number of dead cells at a concentration of 10 μg/ml. These findings were corroborated by morphologic analysis. However, at the lowest concentration (2.5 μg/ml), piplartine-treated cells exhibited typical apoptotic morphological changes. The increase in caspase-3 activity was also observed in lysates of piplartine-treated cells. Rho et al. (2007) using a bioactivity-guided fractionation of MeOH extracts of the fruits of Piper nigrum, isolated the following alkamides: retrofractamide A(1), pipercide (2), piperchabamide D (3), pellitorin (4), dehydroretrofractamide C (5) and dehydropipernonaline (6). The IC50 values for acyl coenzyme A:cholesterol acyltransferase (ACAT), an intracellular enzyme involved in cholesterol accumulation, for the compounds were 24.5 (1), 3.7 (2), 13.5 (3), 40.5 (4), 60 (5) and 90 μM (6), according to the results of an ACAT enzyme assay system using rat liver microsomes. These compounds all inhibited cholesterol esterification in HepG2 (human hepatocellular liver carcinoma) cells.

Hwang et al. (2011) demonstrated that the anti-invasive effects of piperine may occur through inhibition of PKCα (protein kinase Cα) and ERK (extracellular signal-regulated kinase) phosphorylation and reduction of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and AP-1 (activator protein-1) activation, leading to down-regulation of matrix metalloproteinase-9 (MMP-9) expression that was enhanced by phorbol-12-myristate-13-acetate (PMA). Thus, piperine had potential as a potent anticancer drug in therapeutic strategies for fibrosarcoma metastasis.

All compounds alkylamides and piperine derived from black pepper suppressed proin­flammatory transcription factor TNF-induced NF-kappaB activation, but alkyl amides, compound 4 from black pepper and 5 from hot pepper, were most effective (Liu et al. 2010). The human cancer cell proliferation inhibitory activities of piperine and alklyl amides in Capsicum and black pepper were dose dependant. The inhibitory concentrations 50% (IC50) of the alklylamides were in the range 13–200 μg/ml. The extracts of black pepper at 200 μg/ml and its compounds at 25 μg/ml inhibited lipid peroxidation by 45–85%, COX enzymes by 31–80% and cancer cells proliferation by 3.5–86.8%. Overall, these results suggested that black pepper and its constituents exhibited antiinflammatory, antioxidant and anticancer activities.

Piper nigrum roots afforded the following alkaloids: pellitorine, (E)-1-[3′,4′-(methylenedioxy)cinnamoyl]piperidine, 2,4-tetradecadienoic acid isobutyl amide, piperine, sylvamide, cephara­dione A, piperolactam D and paprazine (Ee et al. 2009). Cytotoxic activity screening of the plant extracts indicated some activity. Pellitorine, which was isolated from the roots of Piper nigrum, showed strong cytotoxic activities against HL60 and MCT-7 cell lines (Ee et al. 2010). Microbial transformation of piperine gave a new compound 5-[3,4-(methylenedioxy)phenyl]-pent-2-ene piperidine. Two other alkaloids (E)-1-[3′,4′-(methy­lenedioxy) cinnamoyl]piperidine and 2,4-tetradecadienoic acid isobutyl amide were also found.

Antimutagenic Activity

Black pepper was found to be effective in reducing mutational events induced by and the promutagen agent ethyl carbamate using the wing Somatic Mutation And Recombination Test (SMART) in Drosophila melanogaster (El Hamss et al. 2003). Suppression of metabolic activation or interaction with the active groups of mutagens could be mechanisms by which the spice exerted its antimutagenic action.

Melanocyte Stimulatory Activity

The aqueous extract of black pepper at 0.1 mg/ml was observed to cause nearly 300% stimulation of the growth of a cultured mouse melanocyte line, melan-a, in 8 days (Lin et al. 1999). Piperine (1-piperoylpiperidine), the main alkaloid from Piper nigrum fruit, also significantly stimulated melan-a cell growth. Both Piper nigrum extract and piperine induced morphological alterations in melan-a cells, with more and longer dendrites observed. The augmentation of growth by piperine was effectively inhibited by RO-31-8220, a selective protein kinase C (PKC) inhibitor, suggesting that PKC signalling is involved in its activity. In subsequent studies, amides such as piperine, guineensine and pipericide, from pepper fruits were found to have stimulatory effect on melanocyte proliferation in-vitro and supported the traditional use of P. nigrum extracts in the depigmentary skin disorder, vitiligo (Lin et al. 2007). A crude chloroform extract of P. nigrum containing piperine was more stimulatory than an equivalent concentration of the pure compound, suggesting the presence of other active components. Piperine (1), guineensine (2), pipericide (3), N-feruloyltyramine (4) and N-isobutyl-2E, 4E-dodecadienamide (5) were isolated from the chloroform extract. Their activity was compared with piperine and with commercial piperlongumine (6) and safrole (7), and synthetically prepared piperettine (8), piperlonguminine (9) and 1-(3, 4-methylenedioxyphenyl)-decane (10). Compounds 6–10 either occurred in P. nigrum or were structurally related. Compounds 1, 2, 3, 8 and 9 stimulated melanocyte proliferation, whereas 4, 5, 6, 7 and 10 did not.

A methanolic extract from the leaves of Piper nigrum showed a significant stimulatory effect on melanogenesis in cultured murine B16 melanoma cells (Matsuda et al. 2004). Activity-guided fractionation of the methanolic extract led to the isolation of two known lignans, (-)-cubebin (1) and (-)-3,4-dimethoxy-3,4-desmethylenedioxycubebin (2), together with a new lignan, (-)-3-desmethoxycubebinin (3). Among these lignans, 1 and 2 showed a significant stimulatory activity of melanogenesis without any significant effects on cell proliferation.

Gastrointestinal/Gastroprotective Activity

P. nigrum may protect the colon by decreasing the activity of b-glucuronidase and mucinase. Histopathological studies also showed lesser infiltration into the submucosa, fewer papillae and lesser changes in the cytoplasm of the cells in the rats colon in the black pepper groups (Nalini et al. 1998). Piperazine at doses of 25, 50, 100 mg/kg i.g. dose-dependently protected rats and mice from gastric ulceration induced by stress, indometacin, HCl, and pyloric ligation induced by stress, indometacin, HCl, and pyloric ligation (Bai and Xu 2000). The inhibitory rates were 16.9%, 36.0%, and 48.3% in stress ulcers; 4.4%, 51.1%, and 64.4% in indometacin ulcers; 19.2%, 41.5%, and 59.6% in HCl ulcers; 4.8%, 11.9%, and 26.2% in pyloric ligation ulcers, respectively. Piperazine also inhibited the volume of gastric juice, gastric acidity, and pepsin A activity.

Piperine, an alkaloid of black pepper was found to inhibit gastric emptying of solids/liquids in rats and gastrointestinal transit in mice in a dose and time dependent manner (Bajad et al. 2001). Piperine significantly inhibited gastric emptying of solids and gastrointestinal transit at the doses extrapolated from humans. One week oral treatment of 1 and 1.3 mg/kg in rats and mice, respectively, did not produce a significant change in activity as compared to single dose administration. Gastric emptying inhibitory acti­vity of piperine was independent of gastric acid and pepsin secretion. Piperine was also found to increase gastric secretion in white albino rats (Ononiwu et al. 2002). Increasing the dose from 20 mg/kg weight to 142 mg/kg body weight produced dose dependent increases in gastric acid secretion. When compared with control basal acid secretion, these increases were significant. Piperine was however about 40 times less effective than histamine in increasing gastric acid secretion. In a separate study, piperine (2.5–20 mg/kg, i.p.) was found to dose-dependently reduce castor oil-induced intestinal fluid accumulation (Capasso et al. 2002). The inhibitory effect of piperine was strongly attenuated in capsaicin -treated mice but it was not modified by the vanilloid receptor antagonist capsazepine. The results suggested that piperine reduced castor oil-induced fluid secretion via a mechanism involving capsaicin-sensitive neurons, but not capsazepine-sensitive vanilloid receptors. Results of studies by McNamara et al. (2005) suggested that the effects of piperine at human vanilloid receptor TRPV1 were similar to those of capsaicin except for its propensity to induce greater receptor desensitisation and to exhibit a greater efficacy than capsaicin itself. Piperine also caused greater tachyphylaxis in response to repetitive agonist applications

The medicinal use of pepper and piperine in gastrointestinal motility disorders had been shown to be due to the presence of spasmodic (cholinergic) and antispasmodic (opioid agonist and Ca2+ antagonist) effects (Mehmood and Gilani 2010). When tested in isolated guinea pig ileum, the crude extract of pepper (1–10 mg/ml) and piperine (3–300 μM) caused a concentration-dependent and atropine-sensitive stimulant effect. In rabbit jejunum, pepper extract and piperine relaxed spontaneous contractions, similar to loperamide and nifedipine. In mice, the pepper extract and piperine exhibited a partially atropine-sensitive laxative effect at lower doses, whereas at higher doses it caused antisecretory and anti­diarrheal activities that were partially inhibited in mice pretreated with naloxone, similar to loperamide.

Antiinflammatory Activity

Piperine (1-peperoyl piperidine) isolated from Piper nigrum was found to exhibit antiinflammatory activity in rats in different acute and chronic experimental models like carrageenin-induced rat paw edema, cotton pellet granuloma, and croton oil-induced granuloma pouch (Mujumdar et al. 1990a). Piperine acted significantly on early acute changes in inflammatory processes and chronic granulative changes. Exudative changes in both acute and chronic models, however, were insignificant. The methanolic extract of P. nigrum leaves exhibited antiinflammatory activity (Hirata et al. 2008). Oral administration of the methanolic leaf extract showed a potent dose-dependent inhibition of dinitrofluorobenzene (DNFB)-induced cutaneous reaction at 1 hour [immediate phase response (IPR)] after and 24 hours [late phase response (LPR)] after DNFB challenge in mice which were passively sensitized with anti-dinitrophenyl (DNP) IgE antibody. Ear swelling inhibitory effect of PN-ext on very late phase response (vLPR) in the model mice was significant but weaker than that on IPR. Oral administration of pepper leaf extract inhibited picryl chloride (PC)-induced ear swelling in PC sensitized mice. The extract exhibited in-vitro inhibitory effect on compound 48/80-induced histamine release from rat peritoneal mast cells. Two lignans of the extract, (-)-cubebin and (-)-3,4-dimethoxy-3,4-esmethylen edioxycubebin, were identified as major active principles having histamine release inhibitory activity. Bae et al. (2010) examined the effects of piperine on lipopolysaccharide (LPS)-induced inflammatory responses. Administration of piperine to mice inhibited LPS-induced endotoxin shock, leukocyte accumulation and the production of tumour necrosis factor-alpha (TNF-alpha), but not of interleukin (IL)-1beta and IL-6. In peritoneal macrophages, piperine inhibited LPS/poly (I:C)/CpG-ODN-induced TNF-alpha production. Piperine also inhibited LPS-induced endotoxin shock in TNF-alpha knockout (KO) mice. The results suggested that piperine inhibited LPS-induced endotoxin shock through inhibition of type 1 interferon production.

Antidiabetic Activity

Oral administration of aqueous extract of Piper nigrum seeds and Vinca rosea flowers to alloxan induced diabetic rats once a day for 4 weeks led to significant lowering of blood sugar level and reduction in serum lipids (Kaleem et al. 2005). The decreased levels of antioxidant enzymes, catalase and glutathione peroxidase in alloxan induced diabetic rats were returned to normal in insulin, P. nigrum and V. rosea treated rats. Lipid peroxidation levels were significantly higher in diabetic rats and it was slightly higher in insulin, P. nigrum and V. rosea treated rats as compared to control rat. These results suggested that oxidative stress plays a key role in diabetes, and treatment with P. nigrum and V. rosea were useful in controlling not only the glucose and lipid levels but these components may also be helpful in strengthening the antioxidants potential. Piperine treatment of normal rats enhanced hepatic GSSG (oxidized glutathione) level by 100% and decreased renal GSH (reduced glutathione) concentration by 35% and renal glutathione reductase activity by 25% when compared to normal controls (Rauscher et al. 2000). Treatment of streptozotocin-induced diabetic Sprague-Dawley rats with piperine reversed the diabetic effects on GSSG concentration in the brain, on renal glutathione peroxidase and superoxide dismutase activities, and on cardiac glutathione reductase activity and lipid peroxidation. Piperine treatment did not reverse the effects of diabetes on hepatic GSH concentrations, lipid peroxidation, or glutathione peroxidase or catalase activities; on renal superoxide dismutase activity; or on cardiac glutathione peroxidase or catalase activities. The data indicated that subacute treatment with piperine for 14 days was only partially effective as an antioxidant therapy in diabetes.

Bioassay-guided isolation of chloroform extracts of the fruits of Piper longum and Piper nigum, using an in-vitro DGAT (acyl CoA:diacylglycerol acyltransferase) inhibitory assay, lead to isolation of a new alkamide named (2E,4Z,8E)-N-[9-(3,4-methylenedioxyphenyl)-2,4,8-nonatrienoyl]piperidine (2), together with four known alkamides: retrofractamide C (1), pipernonaline (3), piperrolein B (4), and dehydropipernonaline (5) (Lee et al. 2006). Compounds 2–5 inhibited DGAT with IC50 values of 29.8 (2), 37.2 (3), 20.1 (4), and 21.2 (5)  μM, respectively, but the IC50 value for 1 was more than 900 μM. This finding indicated that compounds possessing piperidine groups (2–5) could be potential DGAT inhibitors. DGAT inhibitors have emerged as a potential therapy for the treatment of obesity and type 2 diabetes.

Hepatoprotective Activity

Piperine, an active alkaloidal constituent of Piper longum and Piper nigrum exerted a significant protection against tert-butyl hydroperoxide and carbon tetrachloride hepatotoxicity by reducing both in vitro and in vivo lipid peroxidation, enzymatic leakage of GPT and AP, and by preventing the depletion of GSH and total thiols in the intoxicated mice (Koul and Kapil 1993), Piperine showed a lower hepatoprotective potency than silymarin. Black pepper was found to have a modulatory effect on the hepatic biotransformation system in mice (Singh and Rao 1993). The results revealed a significant and dose-dependent increase in glutathione S-transferase (GST) and acid-soluble sulfhydryl content in the experimental mice except the one maintained on 0.5% black pepper diet for 10 days. The level of malondialdehyde (MDA) was lowered in the group fed on 2% black pepper diet for 20 days. Being a potential inducer of detoxication system, the possible chemopreventive role of black pepper in chemical carcinogenesis was suggested. The ethanol extract of P. nigrum root was found to be an efficient hepatoprotective and antioxidant agent against CCl4-induced liver injury (Bai et al. 2011). The extract decreased activities of alanine transaminase (ALT) and aspartate transanimase (AST) in rat serum; decreased lipid peroxidation (MDA) and increased glutathione (GSH) % in the rats liver homogenate, as compared with those of the CCl4 positive control rats. The hepato­protective effect of ethanol extract was also supported by the histopathological observations.

Antiatherogenic/Antihyperlipidemic Activity

Administration of the Piper species (Piper guineense, Piper nigrum and Piper umbellatum) for 12 weeks in atherogenic diet fed hamsters prevented the collapse of the antioxidant system and the increase of plasma parameters restoring them towards normality (Agbor et al. 2010). The Piper species also prevented LDL oxidation by increasing the time (lag time) for its oxidation. The atherogenic diet of rodent chow supplemented with 0.2% cholesterol and 10% coconut oil induced a collapse of the erythrocyte anti­oxidant defense system (significant decrease in superoxide dismutase, catalase and glutathione peroxidase activities). The atherogenic diet also induced an increase in plasma total cholesterol, triglyceride, thiobarbituric acid reactive substances (TBARS), oxidation of low density lipoprotein cholesterol (LDL) and accumulation of foam cells in the aorta a hall mark for atherosclerosis. The results suggested that these Piper species had significant antioxidant and antiatherogenic effect against atherogenic diet intoxication.

Studies showed that piperine supplementation appreciably protected erythrocytes from oxidative stress by improving the antioxidant status in high fat diet fed antithyroid drug treated hyperlipidemic rats (Vijayakumar and Nalini 2006a). Concurrent piperine supplementation along with high fat diet and antithyroid drug administration normalized erythrocyte osmotic fragility, reduced lipid peroxidation, and improved the enzymic and non-enzymic antioxidant status compared to those rats that did not receive piperine. Studies also showed that piperine possessed thyrogenic activity, thus modulating apolipoprotein levels and insulin resistance in high fat diet-fed rats, opening a new view in the management of dyslipidemia by dietary supplementation with nutrients (Vijayakumar and Nalini 2006b). The simultaneous administration of piperine and high fat diet significantly reduced plasma lipids and lipoproteins levels, except for HDL, which was significantly elevated. Piperine supplementation also improved the plasma levels of apo A-I, T3, T4, testosterone, and I and significantly reduced apo B, TSH, and insulin to near normal levels.

Antihypertensive Activity

In-vitro studies with rabbit aortic rings showed that piperine possessed a blood pressure-lowering effect mediated possibly through Ca2+ channel blockade (CCB) while consistent fall in blood pressure was restricted by associated vasoconstrictor effect (Taqvi et al. 2008). Additionally, species selectivity existed in the CCB effect of piperine.

Oral administration of piperine in wistar rats was able to partially prevent the increase of blood pressure caused by chronic L-NAME (N(G)-nitro-L-arginine methyl ester) administration (Hlavackova et al. 2010). L-NAME increased the blood pressure, cross-sectional area of aorta, media thickness, elastin and smooth muscle cells actin (SMCA) synthesis and phosphotungstic acid hematoxylin (PTAH) positive myofibrils relative and absolute content in the aortic media, whereas it decreased percentual content of inducible NO synthase (iNOS), elastin and SMCA. Piperine decreased the blood pressure rise from the third week of treatment, synthesis of elastin and the percentual and absolute content of PTAH positive myofibrils, however, it did not affect other para­meters. The authors asserted that the piperine effect was probably caused by the blockage of voltage-dependent calcium channels and supported by filamentous actin disassembly.

Spasmolytic Activity

Black pepper and its main ingredient piperine were found to relieve menorrhalgia in women and supported the use of black pepper by women to relief menorrhalgia in Iranian traditional medicine (Naseri and Yahyavi 2007). The extract reduced the uterus contractions in rats induced by KCl and oxytocin dose dependently. The spasmolytic effect of extract on the KCl-induced contractions was not reduced by L-NAME, phentolamine and naloxone but propranolol reduced the extract activity. In Ca2+-free De Jalon solution with high potassium (60 mM), the extract reduced the contractions induced by cumulative concentrations of CaCl2 dose dependently. The results suggested that the spasmolytic effect of the extract on rat uterus was mediated via voltage dependent calcium channels and β-adrenoceptors could also be involved in this action.

Neuroprotective and CNS Activity

Studies showed that administration of piperine to adult male Wistar rats at a period of 2 weeks before and 1 week after the intracerebroventricular administration of ethylcholine aziridinium ion significantly improved memory impairment and neurodegeneration in hippocampus (Chonpathompikunlert et al. 2010). Piperine also demonstrated neurotrophic effect in hippocampus. The possible underlying mechanisms was postulated to be partly associated with the decrease lipid peroxidation and acetylcholinesterase enzyme. Results of studies by Fu et al. (2010) suggested that the neuroprotective effects of piperine might be associated with suppression of synchronization of neuronal networks, presynaptic glutamic acid release, and Ca2+ overloading. Piperine effectively inhibited the synchronized oscillation of intracellular calcium in rat hippocampal neuronal networks and represses spontaneous synaptic activities in terms of spontaneous synaptic currents (SSC) and spontaneous excitatory postsynaptic currents (sEPSC). Additionally, pretreatment with piperine exerted a protective effect on glutamate-induced decrease of cell viability and apoptosis of hippocampal neurons.

Anticonvulsant, Antidepressant, Sedative and Analgesic Activities

Mori et al. (1985) showed that convulsions of E1 mice were completely suppressed by 60 mg/kg of piperine injected intraperitoneally. The ED50 was 21.1 mg/kg. The brain 5-HT level was significantly higher in the cerebral cortex of piperine treated mice than in control mice. This increase may be related directly to the mechanism of inhibition of convulsions by piperine. In contrast, lower levels of 5-HT were observed in the hippocampus, midbrain and cerebellum. The dopamine level in the piperine treated mice was markedly higher only in the hypothalamus, while the norepinephrine levels were lower in every part of the brain. Amide alkaloids such as ­piperine, pellitorine, 3,4-dimethyinenedioxycinnamoyl-piperidine, and ß-sitesterol isolated from the ethanol extract of Piper nigrum roots showed anticonvulsive, sedative, and analgesic activities to mice (Hu et al. 1996). LD50 of the ethanol and the water extracts to mice were respectively 12.66 and 424.38 g/kg converted into crude material. The anticonvulsant actions of the principal component of pepper, piperine was postulated to underpin the effectiveness of a traditional Chinese medicine, a mixture of radish and pepper in treating epilepsy (D’Hooge et al. 1996). They found that piperine significantly block convulsions induced by intracerebroventricular injection of threshold doses of kainate, but to have no or only slight effects on convulsions induced by L-glutamate, N-methyl-D-aspartate or guanidinosuccinate.

Li et al. (2007) demonstrated the antidepressant-like effects of piperine and its derivative, antiepilepsirine. After 2 weeks of chronic administration, piperine and antiepilepsirine at doses of 10–20 mg/kg significantly reduced the duration of immobility in both forced swimming test and tail suspension test, without accompanying changes in locomotor activity in the open-field test. They elucidated that the antidepressant effect might depend on the augmentation of the neurotransmitter synthesis or the reduction of the neurotransmitter reuptake. Antidepressant properties of piperine were proposed to be mediated via the regulation of serotonergic system, whereas the mechanisms of antidepressant action of antiepilepsirine might be due to its dual regulation of both serotonergic and dopaminergic systems. Wattanathorn et al. (2008) showed that administration of piperine at doses ranging from 5, 10 and 20 mg/kg BW once daily for 4 weeks to male Wistar rats possessed antidepression like activity and cognitive enhancing effect at all treatment duration. The results suggested piperine may be used as potential functional food to improve brain function.

Liao et al. (2009) demonstrated that the antidepressant-like effects of piperine and its mechanisms might be involved by up-regulation of the progenitor cell proliferation of hippocampus and cytoprotective activity. After a week of administration, piperine significantly reduced the duration of immobility forced swimming test and tail suspension test. Piperine exerted protective effect on neuroblastoma cells and increased proliferation of hippocampus neural progenitor cells. Studies showed that piperine significantly reduced the immobility time in the forced swim test and tail suspension test in mice (Mao et al. 2011). Piperine treatment also significantly potentiated the number of head-twitches of mice induced by 5-HTP (a metabolic precursor to 5-HT). The results suggested that the antidepressant-like effect of piperine was mediated via the serotonergic system by enhancing 5-HT (5-hydroxytryptophan) content in mouse brain.

Antithyroid Activity

Daily oral administration (2.50 mg/kg) of piperine to mice for 15 days lowered the serum levels of both the thyroid hormones, thyroxin (T4) and triiodothyronine (T3) as well as glucose concentrations with a concomitant decrease in hepatic 5′D enzyme and glucose-6-phospatase (G-6-Pase) activity (Panda and Kar 2003). However, no significant alterations were observed in animals treated with 0.25 mg/kg of piperine in any of the activities studied except an inhibition in serum T(3) concentration. The decrease in T(4), T(3) concentrations and in G-6-Pase were comparable to that of a standard antithyroid drug, Proylthio­uracil (PTU). The hepatic lipid-peroxidation (LPO) and the activity of endogenous antioxidants, superoxide dismutase (SOD), and catalase (CAT) were not significantly altered in either of the doses (0.25 and 25 mg/kg). It appeared that the action of P. nigrum on thyroid functions was mediated through its active alkaloid, piperine.

Hydrocholagoguic Effect

Administration of black pepper (250 mg/kg b.w.) to rats by gavage caused an increase in bile solids while with other treatments (500 mg black pepper and piperine at 12.5 or 25 mg/kg body weight) bile secretion or dry matter in bile was not changed (Ganesh Bhat and Chandrasekhara 1987). Dietary feeding of black pepper caused an increase in bile flow with a concomitant decrease in bile solids – a hydrocholagoguic effect. Cholesterol and bile acid output were not affected by black pepper or piperine at either level irrespective of the mode of administration; in contrast, the secretion of uronic acids in bile was enhanced by both levels of pepper as also of piperine indicating possible excretion of some of the components of black pepper or of piperine as glucuronides.

Drug Potentiation Activity

Piperine, a major alkaloid isolated from Piper nigrum was found to potentiate pentobarbitone sleeping time in dose dependant manner, with peak effect at 30 minutes (Mujumdar et al. 1990b). Blood and brain pentobarbitone levels were higher in piperine treated animals. Piperine treatment in rats, treated chronically with phenobar­bitone, significantly potentiated pentobarbitone sleeping time, as compared to the controls. There was no alteration in barbital sodium sleeping time. It was postulated that piperine inhibited liver microsomal enzyme system and thereby potentiated the pentobarbitone sleeping time.

Piperine was found to be an inhibitor of multidrug resistance (Li et al. 2011). Piperine could poten­tiate the cytotoxicity of anti-cancer drugs in resistant sublines, such as MCF-7/DOX and A-549/DDP, which were derived from MCF-7 and A-549 cell lines. At a concentration of 50 μM piperine could reverse the resistance to doxorubicin 32.16 and 14.14 folds, respectively. It also re-sensitized cells to mitoxantrone 6.98 folds. Further, long-term treatment of cells by piperine inhibited transcription of the corresponding ABC transporter genes.

Studies showed that piperine inhibited both the drug transporter P-glycoprotein and the major drug-metabolizing enzyme CYP3A4 (Bhardwaj et al. 2002). Piperine inhibited digoxin and cyclosporine A transport in Caco-2 cells with IC50 values of 15.5 and 74.1 μM, respectively. CYP3A4-catalyzed formation of D-617 and norverapamil was inhibited in a mixed fashion. Because both proteins are expressed in enterocytes and hepatocytes and contribute to a major extent to first-pass elimination of many drugs, the data indicated that dietary piperine could affect plasma concentrations of P-glycoprotein and CYP3A4 substrates in humans, in particular if these drugs were administered orally. Two new bisalkaloids, dipiperamides D and E, were isolated as inhibitors of a drug metabolizing enzyme cytochrome P450 (CYP) 3A4 from the white pepper, Piper nigrum (Tsukamoto et al. 2002b). Three new bisalkaloids, dipiperamides A, B, and C, isolated from the white pepper were found to inhibit cytochrome P450 (CYP) 3A4 activity (Tsukamoto et al. 2002a). Dipiperamides D and E showed potent CYP3A4 inhibition with IC50 values of 0.79 and 0.12 μM, respectively, and other metabo­lites from the pepper were mode­rately active or inactive. Of 19 alkamides isolated from Piper nigrum that inhibited human liver microsomal cytochrome P450 2D6 (CYP2D6), compounds 15 and 17 showed more than 50% decrease of the CYP2D6 residual activity after 20 minutes preincubation (Subehan et al. 2006). Both compounds 15 and 17 showed that the charac­te­ristic time- and concentration-dependent inhibition.

Piperine at non-cytotoxic concentrations ranging from 10 to 100 μM, was observed to inhibit P-gp mediated efflux transport of [(3)H]-digoxin across L-MDR1 and Caco-2 cell monolayers (Han et al. 2008). The acute inhibitory effect was dependent on piperine concentration, with abrogation of [(3)H]-digoxin polarized transport attained at 50 μM of piperine. In contrast, prolonged (48 and 72 h) co-incubation of Caco-2 cell monolayers with piperine (50 and 100 μM) increased P-gp activity through an up-regulation of cellular P-gp protein and MDR1 mRNA levels. Peroral administration of piperine at the dose of 112 μg/kg body weight/day to male Wistar rats for 14 consecutive days also increased intestinal P-gp levels. Their data suggested that caution should be exercised when piperine was to be co-administered with drugs that are P-gp substrates, particularly for patients whose diet relies heavily on pepper. In a more recent study, P-glycoprotein (P-gp) inhibitory activity of the aqueous pepper extract was found to be comparable with that of pure piperine and was significantly higher than the alcoholic extract (Aher et al. 2009). Pure piperine and the aqueous extract exhibited significant P-gp inhibitory activity compared with control, which was irrespective of oral pretreatment dose and duration levels. No significant effect of oral pretreatment duration of the aqueous extract was observed. Another recent study showed piperine significantly enhanced the oral exposure of fexofenadine in rats likely by the inhibition of P-glycoprotein-mediated cellular efflux during the intestinal absorption, sugges­ting that the combined use of piperine or piperine-containing diet with fexofenadine may require close monitoring for potential drug-diet interactions (Jin and Han 2010).

Otoprotective Activity

Piperine was found to protect House Ear Institute-Organ of Corti 1 (HEI-OC1) cells against cisplatin-induced apoptosis through the induction of heme oxygenase (HO)-1 expression (Choi et al. 2007). Piperine (10–100 μM) induced the expression of HO-1 in dose- and time-dependent manners. The results demonstrated that the expression of HO-1 by piperine was mediated by both c-Jun N-terminal kinase (JNK) pathway and translocated nuclear factor-E2-related factor-2 (Nrf2).

Antimicrobial Activity

The amide alkaloid constituents isolated from pepper berries namely 2E, 4E, 8Z-N-isobutyleico­satrienamide, pellitorine, trachyone, pergumidiene and isopiperolein B exhibited antimicrobial activity (Reddy et al. 2004). All the isolated compounds were active against Bacillus subtilis, Bacillus sphaericus, and Staphylococcus aureus amongst Gram positive bacteria, and Klebsiella aerogenes and Chromobacterium violaceum among Gram negative bacterial strains. Pepper oil was found to be 100% effective in controlling the mycelial growth of Fusarium graminearum (Singh et al. 2004). The acetone pepper extract retarded 100% mycelial growth of Penicillium viridicatum and Aspergillus ochraceus. The volatile oils from fresh and dried pepper berries and pepper leaves were found to have antimicrobial activity (Sasidharan and Menon 2010). Fresh berry oil (FBO) was found to be more active than standard, tetracycline against Bacillus subtilis and Pseudomonas aeruginosa, on par with reference compound, nystatin against Aspergillus niger but weaker towards Penicillium spp, Candida albicans, Saccharomyces cerevisiae and Trichoderma spp. Dried berry oil (DBO) was more active towards Pseudomonas aeruginosa and Penicillium spp, equal to reference compound against Bacillus subtilis, Candida albicans and Saccharomyces cerevisiae and weaker towards Aspergillus niger and Trichoderma spp. Pepper leaf oil (PLO) was weaker towards all the organisms studied than the references. FBO recorded MIC values of 1 μg/ml for Bacillus subtilis 2.5 μg/ml for Pseudomonas aeruginosa and 8.5 μg/ml for Aspergillus niger. DBO had MIC values of 5 μg/ml for Penicillium spp. and 4 μg/ml for Candida albicans and only 0.8 mug/ml for Saccharomyces cerevisiae. In the case of Trichoderma spp both FBO and DBO required 10 μg/ml. Piperine significantly enhanced accumulation and decreased the efflux of ethidium bromide in Mycobacterium smegmatis, suggesting that it had the ability to inhibit mycobacterial efflux pump (Jin et al. 2011).

ICAM Binding Inhibition Activity

Eight alkamides isolated from the ethanol extracts of the fruits of Piper longum and Piper nigum were elucidated as follows: guineensine (1), retrofracamide C (2), (2E,4Z,8E)-N-[9-(3,4-methylenedioxyphenyl)-2,4,8-nonatrienoyl]piperidine (3), pipernonaline (4), piperrolein B (5), piperchabamide D (6), pellitorin (7), and dehydropipernonaline (8) (Lee et al. 2008). Compounds 3–5, 7, and 8 were found to inhibit potently the direct binding between ICAM-1 (intercellular cell adhesion molecules) and LFA-1 (lymphocyte function associated antigen-1) of THP-1 cells (human monocytic leukaemia cell line) in a dose-dependent manner, with IC50 values of 10.7, 8.8, 13.4, 13.5, and 6.0 μg/ml, respectively.

Immunomodulatory Activity

The purified polysaccharides from Piper nigrum seeds afforded two active fractions PN-Ib and PN-IIa, purified anti-complementary polysaccharides (Chun et al. 2002). PN-Ib had an average molecular mass of 21 kDa contained 88.5% glucose and other negligible minor monosaccharides, while PN-IIa showed a different monosac­charide composition, which contained a signifi­cant proportion of galactose, arabinose, galacturonic acid and rhamnose. None of the anti-complementary activity of any polysaccharide was changed by pronase digestion or polymyxin B treatment, but they were decreased by periodate oxidation. Based upon these results, the usefulness of purified anti-complementary polysaccharides from Piper nigrum was suggested as a supplement for immune enhancement.

Cadmium (Cd), a well known environmental carcinogen, is a potent immunotoxicant; it causes marked thymic atrophy and splenomegaly in rodents and induces apoptosis in murine lymphocytes and alters the immune functions (Pathak and Khandelwal 2007, 2008). Addition of piperine in various concentrations (1, 10 and 50 μg/ml) ameliorated the toxic effects of cadmium. The reported free radical scavenging property of piperine and its antioxidant potential could be responsible for the modulation of intracellular oxidative stress signals. These in turn appeared to mitigate the apoptotic pathway and other cellular responses altered by cadmium. The find-ings strongly indicated the antioxidative, antiapoptotic and chemo-protective ability of piperine in blastogenesis, cytokine release and restoration of splenic cell population indicating its therapeutic usefulness in immuno-compromised situations. In another study, of the three herbals examined for antiimmunotoxic activity, piperine displayed maximum efficacy. All the three doses of piperine (1, 10 and 50 μg/ml) increased cell viability in a dose dependent manner, whereas curcumin and picroliv were also effective, but to a lesser degree. Restoration of ROS and GSH was most prominent with piperine. The antiapoptotic potential was directly proportional to their antioxidant nature. In addition, Cd altered blastogenesis, T and B cell phenotypes and cytokine release were also attenuated best with piperine. The ameliorative potential was in order of piperine  >  curcumin  >  picroliv. Studies by Majdalawieh and Carr (2010) found that black pepper and cardamom exerted immunomodulatory roles and antitumour activities. The black pepper and cardamom aqueous extracts significantly enhanced splenocyte proliferation in a dose-dependent, synergistic fashion. The extracts significantly enhanced the cytotoxic activity of natural killer cells, indicating their potential anti-cancer effects. The findings suggested that black pepper and cardamom constituents could be used as potential therapeutic tools to regulate inflammatory respon­ses and prevent/attenuate carcinogenesis.

Antiandrogenic Activity

The extracts of P. nigrum leaf, P. nigrum fruit and P. cubeba fruit showed potent testosterone 5-alpha reductase inhibitory activity (Hirata et al. 2007). Activity-guided fractionation of P. nigrum leaf extract led to the isolation of (-)-cubebin (1) and (-)-3,4-dimethoxy-3,4-desmethylenedioxycubebin (2). Additionally, it was found that piperine, a major alkaloid amide of P. nigrum fruit, showed potent inhibitory activity, thus a part of the inhi­bitory activity of P. nigrum fruit may depend on piperine. In addition, the P. nigrum leaf extract showed in-vivo antiandrogenic activity using the hair regrowth assay in testosterone sensitive male C57Black/6CrSlc strain mice.

Carcinogenic Effect

Painting and feeding of mice with 2 mg of an extract from black pepper on 3 days a week for 3 months resulted in a significant increase in tumour number of tumour-bearing mice (Shwaireb et al. 1990). Tumour incidence was reduced in those groups of experimental animals receiving 5 or 10 mg Vitamin A-palmitate twice weekly for 3 months by feeding or painting during and subsequent to application of pepper extract. However, feeding of mice with powder of black pepper in diet (50 g/3 kg food) had no impact on carcinogenesis. The researchers (Wrba et al. 1992) found that in mice, injection of safrole, tannic acid (constituents of black pepper) or methylcholanthrene (MCA) during the preweaning period induced tumours in different organs. Safrole and tannic acid were weak carcinogens when compared with MCA which was used as a ­carcinogenic control substance. Force feeding of d-limonene (one of the pepper terpenoids) for a long time to the mice which were injected with any of the above three substances reduced their carcinogenic activity, while force feeding of piperine (one of black pepper alkaloids) was ineffective.

Insecticidal Activity

Several insecticidal amides, such as pipericide, (E,E)-N-(2-methylpropyl)-2,4,12-tridecadi­enamide, and (E,E,E)-11-(1,3-benzodioxol-5-yl)-N-(2-methylpropyl)- 2,4,10-undecatrien-amide, had been isolated from P. nigrum (Miyakado et al. 1979; Su and Horvat 1981). The amide alkaloids from pepper fruit such as pellitorine, guineensine, pipercide, and retrofractamide exhibited insecticidal activity against third instar larvae of Culex pipiens pallens, Aedes aegypti, and Aedes togoi (Park et al. 2002). The compound most toxic to C. pipiens pallens larvae was pipercide (0.004 ppm) followed by retrofractamide A (0.028 ppm), guineensine (0.17 ppm), and pellitorine (0.86 ppm). Piperine (3.21 ppm) was least toxic. Against A. aegypti larvae, larvicidal activity was more pronounced in retrofractamide A (0.039 ppm) than in pipercide (0.1 ppm), guinee­nsine (0.89 ppm), and pellitorine(0.92 ppm). Piperine (5.1 ppm) was relatively ineffective. Against A. togoi larvae, retrofractamide A (0.01 ppm) was much more effective, compared with pipercide (0.26 ppm), pellitorine (0.71 ppm), and guineensine (0.75 ppm). Again, very low acti­vity was observed with piperine (4.6 ppm). A new insecticidal amide piptigrine possessing highly extended conjugation was isolated from the dried ground seeds of Piper nigrum along with the known amides piperine and wisanine (Siddiqui et al. 2004a). Piptigrine exhibited toxicity of 15.0 ppm against fourth instar larvae of Aedes aegypti Liston. Pipsaeedine and pipbinine from ground pepper fruit exhibited toxicities of 45.0 and 40.0 ppm, respectively, against fourth instar larvae of Aedes aegypti (Siddiqui et al. 2004b). Pipnoohine and pipyahyine from dried ground whole pepper fruits exhibited toxicity at 35.0 and 30.0 ppm respectively against fourth instar larvae of Aedes aegypti (Siddiqui et al. 2004c).

The petroleum ether and ethyl acetate fractions of dried ground seeds of Piper nigrum afforded 16 compounds (1–16) including one new insecticidal amide, pipwaqarine elucidated as 1-[13-(3′,4′-methylenedioxyphenyl)-2E,4E,12E-tridecatrienoyl]-N-isopentylamide, and six constituents (3,4,6,7,11,15) (Siddiqui et al. 2005). Pipwaqarine exhibited toxicity of 30 ppm against fourth instar larvae of Aedes aegypti. Fractionation of Piper nigrum ethanol extract, yielded the larvicidal amides piperolein-A and piperine (Simas et al. 2007). Comparing LC50 values, the ethanol extract (0.98 ppm) was the most toxic, followed by piperolein-A (1.46 ppm) and piperine (1.53 ppm). Ethanolic extracts of dried fruits of three species of peppercorns: Long pepper, Piper longum, black pepper, Piper nigrum, and white pepper, Piper nigrum exhibited the larvicidal activity against the different instars of field-collected Indian strain of dengue fever mosquito Aedes aegypti (Kumar et al. 2010, 2011). Against early fourth instar, the ethanolic extracts of Black and White P. nigrum proved to be 30–40% less toxic than the extracts of P. longum, whereas against third instars, white pepper extracts exhi­bited 7% more efficacy than that of black pepper and 47% more toxicity than that of long pepper. The results also revealed that the extracts of all the three pepper species were 11–25 times more toxic against the third instar larvae as compared to the early fourth instars. It was observed, however, that the larvae of Ae. aegypti were most susceptible against a mixture of the three extracts when taken in 1:1:1. The larvae treated with all the pepper species showed initial abnormal behavior in their motion followed by excitation, convulsions, and paralysis, leading to 100% kill indicating delayed larval toxicity and effects of the extracts on the neuromuscular system.

N-isobutylamide alkaloids (pellitorine, guineensine, pipercide and retrofractamide A) derived from P. nigrum were found to have insecticidal activity (Park 2011). On the basis of 24-hour LD50 values, the compound most toxic to female Culex pipiens pallens was pellitorine (0.4 μg/female) followed by guineensine (1.9 μg/ female), retrofractamide A (2.4 μg/ female) and pipercide (3.2 μg/ female). LD50 value of chlorpyrifos was 0.03 μg/ female. Against female Aedes aegypti, the insecticidal activity was more pronounced in pellitorine (0.17 μg/ female) than in retrofractamide A (1.5 μg/ female), guineensine (1.7 μg/ female), and pipercide (2.0 μg/ female). LD50 value of chlorpyrifos was 0.0014 μg/ female.

Traditional Medicinal Uses

Like all eastern spices, pepper was historically both a seasoning and a medicine. The pungency in pepper is due to the piperine compound. Black peppercorns have featured in traditional remedies in Ayurvedic, Unani and Siddha medicine in India for centuries and in Jamu preparations in Indonesia. It has been prescribed for illnesses such as constipation, diarrhoea, earache, gangrene, heart disease hernia, indigestion, insect bites, insomnia, joint pains, lung diseases, liver problems, tooth decay and toothache. Various sources also recommend pepper to treat eye problems, often by applying salves or poultices made with pepper directly to the eye.

Other Uses

Pepper oil is a constituent in certain perfumes and some famous brands includes ‘Charlie’ of Revlon and ‘Poison’ of Christian Dior. In the past, Egyptians used it in embalming mixture and also as an air-purifier. Its insecticidal properties are also being exploited for household use and agriculture.

Piper nigrum has insecticidal potential. Toxicity (mortality) of Piper nigrum extracts against the larva of Spodoptera litura in decreasing order were: hexane (LD50: 1.8 mg/g)  >  acetone (LD50: 18.8 mg/g)  >  chloroform (LD50: NA, the toxicity was very low)  >  essential oil (no mortality) (Fan et al. 2011). Insect development and growth index observations showed that the hexane extract had antifeedant properties resulting in severe growth inhibition of Spodoptera litura.

Comments

Vietnam is the world’s leading producer and exporter of pepper, producing 34% of the world’s Piper nigrum. Other main producers include India (19%), Brazil (13%), Indonesia (9%), Malaysia (8%), Sri Lanka (6%), China (6%), and Thailand (4%).